Fibrochondrogenesis is a congenital disorder presenting several features and radiological findings, some which distinguish it from other osteochondrodysplasias. These include: fibroblastic dysplasia and fibrosis of chondrocytes (cells which form cartilage); and flared, widened

long bone metaphyses (the portion of bone that grows during childhood).

Other prominent features include dwarfism, shortened ribs that have a appearance, micrognathism (severely underdeveloped jaw), macrocephaly (enlarged head), thoracic hypoplasia (underdeveloped chest), enlarged stomach, platyspondyly (flattened spine), and the somewhat uncommon deformity of tongue (in which the tongue appears split, resembling that of a reptile).

Despite this excess bone formation, people with osteopetrosis tend to have bones that are more brittle than normal. Mild osteopetrosis may cause no symptoms, and present no problems.

However, serious forms can result in...

- Stunted growth, deformity, and increased likelihood of fractures

- Patients suffer anemia, recurrent infections, and hepatosplenomegaly due to bone expansion leading to bone marrow narrowing and extramedullary hematopoiesis

- It can also result in blindness, facial paralysis, and deafness, due to the increased pressure put on the nerves by the extra bone

- Abnormal cortical bone morphology

- Abnormal form of the vertebral bodies

- Abnormality of temperature regulation

- Abnormality of the ribs

- Abnormality of vertebral epiphysis morphology

- Bone pain

- Cranial nerve paralysis

- Craniosynostosis

- Hearing impairment

- Hypocalcemia

Collagen improperly formed, enough collagen is made but it is defective.

- Bones fracture easily, sometimes even before birth

- Bone deformity, often severe

- Respiratory problems possible

- Short stature, spinal curvature and sometimes barrel-shaped rib cage

- Triangular face

- Loose joints (double-jointed)

- Poor muscle tone in arms and legs

- Discolouration of the sclera (the 'whites' of the eyes are blue)

- Early loss of hearing possible

Type III is distinguished among the other classifications as being the "progressive deforming" type, wherein a neonate presents with mild symptoms at birth and develops the aforementioned symptoms throughout life. Lifespans may be normal, albeit with severe physical handicapping.

Opsismodysplasia can be characterized by a delay in bone maturation, which refers to "bone aging", an expected sequence of developmental changes in the skeleton corresponding to the chronological age of a person. Factors such as gender and ethnicity also play a role in bone age assessment. The only indicator of physical development that can be applied from birth through mature adulthood is bone age. Specifically, the age and maturity of bone can be determined by its state of ossification, the age-related process whereby certain cartilaginous and soft tissue structures are transformed into bone. The condition of epiphyseal plates (growth plates) at the ends of the long bones (which includes those of the arms, hands, legs and feet) is another measurement of bone age. The evaluation of both ossification and the state of growth plates in children is often reached through radiography (X-rays) of the carpals (bones of the hand and wrist). In opsismodysplasia, the process of ossification in long bones can be disrupted by a failure of ossification centers (a center of organization in long bones, where cartilage cells designated to await and undergo ossification gather and align in rows) to form. This was observed in a 16-month-old boy with the disorder, who had no apparent ossification centers in the carpals (bones of the hand and wrist) or tarsals (bones of the foot). This was associated with an absence of ossification in these bones, as well as disfigurement of the hands and feet at age two. The boy also had no ossification occurring in the lower femur (thigh bone) and upper tibia (the shin bone).

The differential diagnosis of osteopetrosis includes other disorders that produce osteosclerosis. They constitute a wide array of disorders with clinically and radiologically diverse manifestations. Among the differential diagnosis are hereditary ostoesclerosing dysplasias such as; neuropathic infantile osteopetrosis, infantile osteopetrosis with renal tubular acidosis, infantile osteopetrosis with immunodeficiency, infantile osteopetrosis with leukocyte adhesion deficiency syndrome (LAD-III), pyknodysostosis (osteopetrosis acro-osteolytica), osteopoikilosis (Buschke–Ollendorff syndrome), osteopathia striata with cranial sclerosis, mixed sclerosing skeletal dysplasias, progressive diaphyseal dysplasia (Camurati–Engelmann disease), SOST-related sclerosing skeletal dysplasias. Besides, the differential diagnosis includes acquired conditions that induce osteosclerosis such as osteosclerotic metastasis notably carcinomas of the prostate gland and breast, Paget's disease of bone, myelofibrosis (primary disorder or secondary to intoxication or malignancy), Erdheim-Chester disease, osteosclerosing types of osteomyelitis, sickle cell disease, hypervitaminosis D and hypoparathyroidism.

Collagen quantity is sufficient but is not of a high enough quality

- Bones fracture easily, especially before puberty

- Short stature, spinal curvature, and barrel-shaped rib cage

- Bone deformity is mild to moderate

- Early loss of hearing

Similar to Type I, Type IV can be further subclassified into types IVA and IVB characterized by absence (IVA) or presence (IVB) of dentinogenesis imperfecta.

The distinctive characteristics of OSMED include severe bone and joint problems and very severe hearing loss. This disorder affects the epiphyses, the parts of the bone where growth occurs. People with the condition are often shorter than average because the bones in their arms and legs are unusually short. Other skeletal signs include enlarged joints, short hands and fingers, and flat bones of the spine (vertebrae). People with the disorder often experience back and joint pain, limited joint movement, and arthritis that begins early in life. Severe high-tone hearing loss is common. Typical facial features include protruding eyes; a sunken nasal bridge; an upturned nose with a large, rounded tip; and a small lower jaw. Some affected infants are born with an opening in the roof of the mouth, which is called a cleft palate.

Gerodermia osteodysplastica is characterized by symptoms and features which affect the connective tissues, skin and skeletal system.

These are: wrinkly, loose skin over the face, abdomen, and extremites (hands, feet) on the dorsal sides usually worsened by chronic joint laxity and hyperextensibility; fragmented elastic fibers of the skin that are reduced in number, with disorientation of collagen fibers; osteopenia and osteoporosis, with associated fractures; malar hypoplasia (underdeveloped cheek bone), maxillary hypoplasia (underdeveloped upper jaw), mandibular prognathism (protrusion of the lower jaw and chin), bowed long bones, platyspondyly (flattened spine) related to vertebral collapse; kyphoscoliosis (scoliosis with kyphosis, or "hunch back"), metaphyseal peg (an unusual outgrowth of metaphyseal tissue which protrudes into the epiphyseal region of the bone, near the knee); and the overall physical effects and facial appearance of dwarfism with premature aging.

Other features and findings include: intrauterine growth retardation, congenital hip dislocations, winged scapulae (shoulder blades), pes planus (fallen arches), pseudoepiphyses of the second metacarpals (upper bone of the fingers), hypotelorism (close-set eyes), malformed ears,

developmental delay,

failure to thrive and abnormal electroencephalograph (EEG) readings.

Dental and orthodontal abnormalities in addition to maxillary hypoplasia and mandibular prognathism have also been observed in gerodermia osteodysplastica. Including malocclusion of the dental arches (the maxilla and mandible), radiological findings in some cases have indicated significant overgrowth of the mandibular premolar and molar roots;

hypercementosis (overproduction of cementum) of the molars and maxillary incisors; enlarged, funnel-shaped mandibular lingula (spiny structures on the ramus of the mandible); and a radiolucent effect on portions of many teeth, increasing their transparency to x-rays.

Prenatal and neonatal diagnosis of boomerang dysplasia includes several prominent features found in other osteochondrodysplasias, though the "boomerang" malformation seen in the long bones is the delineating factor.

Featured symptoms of boomerang dysplasia include: dwarfism (a lethal type of infantile dwarfism caused by systemic bone deformities), underossification (lack of bone formation) in the limbs, spine and ilium (pelvis); proliferation of multinucleated giant-cell chondrocytes (cells that produce cartilage and play a role in skeletal development - chondrocytes of this type are rarely found in osteochondrodysplasias), brachydactyly (shortened fingers) and (undersized, shortened bones).

The characteristic "boomerang" malformation presents intermittently among random absences of long bones throughout the skeleton, in affected individuals. For example, one individual may have an absent radius and fibula, with the "boomerang" formation found in both ulnas and tibias. Another patient may present "boomerang" femora, and an absent tibia.

Fibrochondrogenesis is a rare autosomal recessive form of osteochondrodysplasia, causing abnormal fibrous development of cartilage and related tissues.

It is a lethal rhizomelic (malformations which result in short, underdeveloped limbs) form of dwarfism, exhibiting both skeletal dysplasia (malformations of bone) and fibroblastic dysplasia (abnormal development of fibroblasts, specialized cells that make up fibrous connective tissue, which plays a role in the formation of cellular structure and promotes healing of damaged tissues). Death caused by complications of fibrochondrogenesis occurs in infancy.

Melorheostosis is a mesenchymal dysplasia manifesting as regions of dripping wax appearance or flowing candle wax appearance. It is thought to be caused by a mutation of the LEMD3 gene. The disorder can be detected by radiograph due to thickening of bony cortex resembling "dripping candle wax". It is included on the spectrum of developmental bone dysplasias including pycnodysostosis and osteopoikilosis. The disorder tends to be unilateral and monostotic (i.e. affecting a single bone), with only one limb typically involved. Cases with involvement of multiple limbs, ribs, and bones in the spine have also been reported. There are no reported cases of involvement of skull or facial bones. Melorheostosis can be associated with pain, physical deformity, skin and circulation problems, contractures, and functional limitation. It is also associated with a benign inner ear dysplasia known as osteosclerosis.

It is not known if LEMD3 mutations can cause isolated melorheostosis in the absence of Buschke-Ollendorff syndrome.

"Maffucci syndrome" is a sporadic disease characterized by the presence of multiple enchondromas associated with multiple simple or cavernous soft tissue hemangiomas. Also lymphangiomas may be apparent.

Patients are normal at birth and the syndrome manifests during childhood and puberty. The enchondromas affect the extremities and their distribution is asymmetrical.

Opsismodysplasia is a type of skeletal dysplasia (a bone disease that interferes with bone development) first described by Zonana and associates in 1977, and designated under its current name by Maroteaux (1984). Derived from the Greek "opsismos" ("late"), the name "opsismodysplasia" describes a delay in bone maturation. In addition to this delay, the disorder is characterized by (short or undersized bones), particularly of the hands and feet, delay of ossification (bone cell formation), platyspondyly (flattened vertebrae), irregular metaphyses, an array of facial aberrations and respiratory distress related to chronic infection. Opsismodysplasia is congenital, being apparent at birth. It has a variable mortality, with some affected individuals living to adulthood. The disorder is rare, with an incidence of less than 1 per 1,000,000 worldwide. It is inherited in an autosomal recessive pattern, which means the defective (mutated) gene that causes the disorder is located on an autosome, and the disorder occurs when two copies of this defective gene are inherited. No specific gene has been found to be associated with the disorder. It is similar to spondylometaphyseal dysplasia, Sedaghatian type.

Hajdu–Cheney syndrome causes many issues with an individual’s connective tissues. Some general characteristics of an individual with Hajdu–Cheney syndrome include bone flexibility and deformities, short stature, delayed acquisition of speech and motor skills, dolichocephalic skull, Wormian bone, small maxilla, hypoplastic frontal sinuses, basilar impression, joint laxity, bulbous finger tips, and severe osteoporosis. Wormian bone occurs when extra bones appear between cranial sutures. Fetuses with Hajdu–Cheney syndrome often will not be seen to unclench their hands on obstetrical ultrasound. They may also have low-set ears and their eyes may be farther apart than on a usual child, called hypertelorism. Children's heads can have some deformities in their shape and size (plagiocephaly). Early tooth loss and bone deformities, such as serpentine tibiae and fibulae, are also common in those affected.

The appearance of people with the disorder is caused by a loss of bone in the mandible which the body replaces with excessive amounts of fibrous tissue. In most cases, the condition fades as the child grows, but in a few even rarer cases the condition continues to deform the affected person's face. Cherubism also causes premature loss of the primary teeth and uneruption of the permanent teeth.

The condition Cherubism is a rare autosomal dominant disease of the maxilla and mandible. Approximately 200 cases have been reported by medical journals with the majority being males. Cherubism is usually first diagnosed around age 7 and continues through puberty and may or may not continue to advance with age. The degrees of Cherubism vary from mild to severe. Osteoclastic and osteoblastic remodeling contributes to the change of normal bone to fibrous tissue and cyst formation. As noted by the name, the patient's face becomes enlarged and disproportionate due to the fibrous tissue and atypical bone formation. The sponge-like bone formations lead to early tooth loss and permanent tooth eruption problems. The condition also affects the orbital area, creating an upturned eye appearance. The cause of cherubism is believed to be traced to a genetic defect resulting from a mutation of the SH3BP2 gene from chromosome 4p16.3. While the condition is rare and painless, the afflicted suffer the emotional trauma of disfigurement. The effects of Cherubism may also interfere with normal jaw motion and speech. Currently, removal of the tissue and bone by surgery is the only treatment available. This condition is also one of the few that unexpectedly stops and regresses. Normal bone remodeling activity may resume after puberty.

Cherubism is displayed with genetic conformation and when excessive osteoclasts are found in the affected areas of the mandible and maxilla. Large cysts will be present with excessive fibrous areas inside the bone. The fibers and cysts will be found among the trabecula of the Coronoid process, the ramus of mandible, the body of mandible and the maxilla regions. The maxilla will be affected up to and including the orbits and sometimes inside the lower orbits. The maxilla and zygomatic bones are depressed and eyes appear to gaze upward. The maxilla has been found to be more severely affected in most cases than the mandible bone. Some patients found with lower inner orbital growths and cysts may lose vision.

Pycnodysostosis causes the bones to be abnormally dense (osteopetrosis); the last bones of the fingers (the distal phalanges) to be unusually short; and delays the normal closure of the connections (sutures) of the skull bones in infancy, so that the "soft spot" (fontanelle) on top of the head remains widely open.

Those with the syndrome have brittle bones which easily break, especially in the legs and feet. The jaw and collar bone (clavicle) are also particularly prone to fractures.

Other abnormalities involve the head and face, teeth, collar bones, skin, and nails. The front and back of the head are prominent. Within the open sutures of the skull, there may be many small bones (called wormian bones). The midface is less full than usual. The nose is prominent. The jaw can be small. The palate is narrow and grooved. The baby teeth are late coming in and may be lost much later than usual. The permanent teeth can also be slow to appear. The permanent teeth are commonly irregular and teeth may be missing (hypodontia). The collar bones are often underdeveloped and malformed. The skin over the back of the fingers is very wrinkled. The nails are flat and grooved.

Pycnodysostosis also causes problems that may become evident with time. Aside from the broken bones, the distal phalanges and the collar bone can undergo slow progressive deterioration. Vertebral defects may permit the spine to curve laterally resulting in scoliosis. The dental problems often require orthodontic care and cavities are common.

"Cleidocranial dysostosis" is a general skeletal condition named for the collarbone (cleido-) and cranium deformities which people with it often have. Common features include:

- Partly or completely missing collarbones.

- A soft spot or larger soft area in the top of the head where the fontanelle failed to close.

- Bones and joints are underdeveloped.

- The permanent teeth include supernumerary teeth.

- Permanent teeth not erupting

- Bossing (bulging) of the forehead.

- Hypertelorism

The following are symptoms characteristic with individuals having the disorder. Individuals may display some, most, or all of these symptoms throughout the course of their life, though symptoms may vary with each patient.

- Abnormal hair (coarse, thick, brittle)

- Calvarial hypomineralization (soft skull)

- Y-shaped cataracts by 1–2 years of age

- Skeletal defects

- Hypertelorism (wide-set eyes)

- Facial dysmorphisms

- Late-closing fontanels

- Abnormal accumulation of proteins in the endoplasmic reticulum

- Scoliosis

- Broad forehead, nose

- Missing, small teeth or abnormal teeth positioning

- Poor skull calcification

- Flat foot

- Motor delay

- Abnormal vertebrae

- Prominent forehead and brow

- High nose bridge

- Capillary hemangioma

- Delayed tooth eruption

- Long upper lip groove

- Large mouth

- High arched palate

- Narrow hips and rib cage

- Thin lips

- Narrow and sloping shoulders

- Hyperpigmentation

- Hyperextensible joints

Onset of the disease is in neonatal development and infancy, and symptoms tend to become evident soon after birth.

Hair abnormalities are very prominent in majority of the cases of TDO. Kinky/curly hair that is unusually dry and easily sheds is present at birth. In 80% of cases, the hair has a more relaxed appearance by adolescence. The presence of this hair texture type is a defining characteristic between a diagnosis of TDO verses amelogenesis imperfecta with hypomaturation. Additionally, in TDO the nails are usually abnormally thin, brittle, and split frequently. Cranial deficiencies are marked by the presence of having a long skull relative to its width, or protrusive foreheads due to increased thickness of the cranial bones and premature closing of the associated sutures in the skull. The long bones in the body (arms, legs) are also abnormally long and tend to fracture very easily. Osteosclerosis, commonly seen in TDO cases is characterized by an increase in bone density, affecting the skull and the mastoid process located behind the jawbone on the skull, as well as a shortened ramus seen in people with TDO. There are no known pathological problems associated with hair and bone changes in people with this disease. Changes in the long bones tend to appear later in development, but changes in the teeth appear once the teeth being to form, called primary dentition. The hair and bone abnormalities are evaluated radiographically during initial diagnosis, and visually during the course of the disease. Radiographic exams may be repeated if there is suspect of fracture.

Cherubism is a rare genetic disorder that causes prominence in the lower portion in the face. The name is derived from the temporary chubby-cheeked resemblance to putti, often confused with cherubs, in Renaissance paintings.

Boomerang dysplasia is a lethal form of osteochondrodysplasia known for a characteristic congenital feature in which bones of the arms and legs are malformed into the shape of a boomerang. Death usually occurs in early infancy due to complications arising from overwhelming systemic bone malformations.

Osteochondrodysplasias are skeletal disorders that cause malformations of both bone and cartilage.

Osteoporosis is due to causal factors like atrophy of disuse and gonadal deficiency. Hence osteoporosis is common in post menopausal women and in men above 50 yrs. Hypercorticism may also be causal factor, as osteoporosis may be seen as a feature of Cushing's syndrome.

Metabolic bone disease is an umbrella term referring to abnormalities of bones caused by a broad spectrum of disorders.

Most commonly these disorders are caused by abnormalities of minerals such as calcium, phosphorus, magnesium or vitamin D leading to dramatic clinical disorders that are commonly reversible once the underlying defect has been treated. These disorders are to be differentiated from a larger group of genetic bone disorders where there is a defect in a specific signaling system or cell type that causes the bone disorder. There may be overlap. For example, genetic or hereditary hypophosphatemia may cause the metabolic bone disorder osteomalacia. Although there is currently no treatment for the genetic condition, replacement of phosphate often corrects or improves the metabolic bone disorder.

Melorheostosis is a medical developmental disorder and mesenchymal dysplasia in which the bony cortex widens and becomes hyperdense in a sclerotomal distribution. The condition begins in childhood and is characterized by thickening of the bones. Pain is a frequent symptom and the bone can have the appearance of dripping candle wax.

Gerodermia osteodysplastica (GO), also called geroderma osteodysplasticum and Walt Disney dwarfism, is a rare autosomal recessive connective tissue disorder included in the spectrum of cutis laxa syndromes.

Usage of the name "Walt Disney dwarfism" is attributed to the first known case of the disorder, documented in a 1950 journal report, in which the authors described five affected members from a Swiss family as having the physical appearance of dwarves from a Walt Disney film.

The terms "geroderma" or "gerodermia" can be used interchangeably with "osteodysplastica" or "osteodysplasticum", with the term "hereditaria" sometimes appearing at the end.